The present invention relates to the field of drilling in ground, in particular for the purpose of constructing foundations, such as for example continuous screens constituted by juxtaposed concrete wall elements.
The invention relates more precisely to a drilling machine for excavating in ground in a drilling direction that is substantially vertical, and more particularly in hard soil.
More particularly, the invention relates to a machine having both a bottom portion provided with cutter members and also a top portion, the drilling machine presenting a longitudinal direction extending between the top portion and the bottom portion of the drilling machine, the drilling machine comprising:
an anchor module having a front face and a rear face, the anchor module comprising at least one anchor device having at least one front anchor pad arranged on the front face and at least one rear anchor pad arranged on the rear face, the front and rear anchor pads being deployable in a deployment direction that extends transversely to the longitudinal direction of the drilling machine so as to bear against walls of the excavation in order to hold the anchor module stationary in the ground; and
a drilling module carrying the cutter members, the drilling module co-operating with the anchor module.
That type of drilling machine is generally used for drilling in hard soil, e.g. in granite. The movement device serves to exert additional thrust on the drilling tools, for the purpose of facilitating excavation.
Such a machine is described in particular in EP 0 811 724. It can be understood that the anchor module serves to hold the drilling machine stationary in the excavation. Nevertheless, that drilling machine does not make it possible effectively to correct the drilling path. Correcting the drilling path of the drilling machine requires its position in the trench to be modified. After modifying its position, the drilling machine is generally no longer centered in the excavation but is closer to one of the larger walls than it is to the opposite wall. Also, deploying anchor pads has the effect of recentering the drilling machine in the excavation, thereby modifying the position of the machine, and consequently once more skewing the drilling path.